Inasmuch as optical fibers are characterized by a wide transmission bandwidth and relatively low attenuation, they are particularly well-suited for communications applications. However, optical fiber interfaces to electronic and optical networks tend to be expensive to manufacture—usually as a result of the difficulty associated with mounting optical transmitting and receiving devices on a substrate and separately aligning each one of these devices with an optical fiber. For this reason, optical fiber technology has been widely implemented in long-haul communications systems where the interfaces are relatively few. However, the high cost of manufacturing fiber optic interfaces has been a barrier that has slowed the penetration of the fiber optic technology into other markets, such as local metropolitan area communication networks, for example.
A typical single mode fiber has a core diameter of approximately nine microns, while a multimode fiber has a core diameter of approximately 50 or 62.5 microns. Because of the small dimensions of optical fiber cores, aligning optical fibers with optical transmitting devices, which have aperture sizes that vary from approximately 2 to 10 microns, is difficult. Obviously, the problem is particularly acute when the optical devices are to be aligned with single mode fiber.
Many efforts have been made to incorporate alignment schemes between a fiber array and an array of corresponding waveguides on a planar photonic subassembly. One such effort is described in U.S. Pat. No. 5,482,585, issued to Ota et al. on Jan. 9, 1996 and entitled “Process for Optically Joining an Optical fiber Array to an Opponent Member”. The Ota et al. patent describes a method in which an optical fiber array is initially formed by affixing optical fibers between a V-grooved base plate and a similarly-grooved top plate. The optical fibers of the optical fiber array are optically joined to an optical substrate (i.e., the “opponent member”) by using, as a joining reference surface, either one of a first surface of the fixing base plate at which the optical fibers are fixed and a second surface of the fixing base plate opposite to the surface.
Another effort is described in U.S. Pat. No. 5,339,876 issued to Kakii et al. on Aug. 16, 1994 and entitled “Grooved Optical Fiber Connection Incorporating Elastic Guide Pin Pressing Members”. The Kakii et al. patent describes an optical connector for connecting optical fibers comprising a guide-groove substrate having grooves for positioning optical fibers and guide pins; an upper plate having groove portions each for covering the guide pins positioned in the guide grooves of the guide-groove substrate; elastic guide-pin pressing members each provided in the groove portions of the upper plate above portions where the guide pin grooves are in contact with the guide pins.
U.S. Pat. No. 7,587,108 issued to B. S. Carpenter et al. on Sep. 8, 2009 discloses an arrangement for attaching a “cantilevered” fiber array to a planar lightwave circuit. In particular, the cantilevered fiber array comprises a base member for supporting the fiber array, with a cover lying over the base member, where a terminal end of the fiber array extends beyond an end of at least one of the cover or base, forming a cantilevered structure. The terminal end of the fiber array is then disposed in an alignment groove formed in the planar lightwave circuit to provide optical coupling between the fiber array and the optics formed in planar lightwave circuit.
While such efforts provided some means of alignment between a fiber array and a waveguide array, there remains a need for an arrangement for interconnecting a fiber array with a planar photonic subassembly that permits the use of low-cost alignment techniques, while relaxing manufacturing tolerances on the various components and permitting the use of inexpensive materials (such as plastics) for at least a portion of the structure.